Patent GB-913524-A (GB)
Title: A process for the alkylation of phenols
Inventor: SHIMMIN JAMES DONALD
IPC: C07C37/18
Filed: 1960-06-10
Abstract: A process for preparing an alkyl phenol comprises contacting a phenol with an alkylating agent in the presence of a catalyst comprising a metal hydride or an organo-metallic compound of the general formula MRn, in which M represents a metal of Group 1, 2 or 3 of the Periodic Table, R represents a hydrogen atom, an alkyl group, an aryl group, an alkoxide group, an aralkyl group or an aralkoxy group and n is the valency of the metal M, providing that when n is 2 each symbol R can be the same or different and when n is 3 each symbol R can be the same or different or two of the symbols R can be the same.  A "phenol" is defined as any aromatic compound containing a phenolic hydroxyl group i.e. a compound in which one or more hydroxyl groups are attached directly to the aromatic nucleus, providing the compound has at least one unsubstituted hydrogen atom attached directly to a carbon atom in the aromatic nucleus for every alkyl group it is desired to introduce into the nucleus during alkylation process. Suitable phenols are the monohydric phenols, for instance phenol itself; the alkyl substituted phenols, for instance the cresols; the xylenols 2,4-dimethyl phenol; 2,6-di-tert butyl phenol; the halo-substituted phenols, for instance, p-chlorophenol, and 2-amino-4-bromo phenol; dihydric phenols such as catechol, halo, amino- or nitro - catechols, 2,3 - dihydroxytoluene, resorcinol, hydroquinone, 4-amino resorcinol; trihydric phenols such as pyrogallol and phloroglucinol, and tetrahydric phenols such as 1,2,3,4-tetrahydroxybenzene, other suitable phenols include the naphthols, e.g. alpha- or beta-naphthol; their homologues, di- and tri-hydroxynaphthalenes; hydroxy anthracenes; and hydroxy phenanthrenes and poly phenols e.g. a bis phenol.  The alkylating agents which may be used are acetylene, substituted acetylene, mono-olefine, conjugated or non-conjugated poly- or cyclo-olefine, for example isoprene, cyclohexene or methyl cyclohexene, aryl substituted conjugated or non-conjugated olefine, halogen substituted olefine, primary, secondary or tertiary alkyl halide, polyhaloalkane, halocycloalkane or aralkyl halide and in addition other compounds having a double or triple bond between adjacent carbon atoms such as an unsaturated alcohol, amine, ester or ether.  Although Group 1 or 2 metal compounds can be used as catalysts for example compounds of lithium, sodium, potassium or copper, or magnesium, calcium, barium or zinc, a Group 3 metal compound especially an aluminium compound is preferred.  Suitable metal alkyls are the methyls, ethyls, isobutyls of a Group 1, 2 or 3 metal, whilst suitable alkoxides include the ethoxides and propoxides of such metals.  The aryls and aralkyls which may be used include the phenyls, benzyls or toluyls of the Group 1, 2 or 3 metal and the aralkoxy compound include the benzoxides of such metals.  Examples of such compounds and of the hydrides which may be used include lithium hydride, sodium hydride, potassium ethyl, potassium ethoxide, calcium hydride, barium dimethyl, zinc diethyl, gallium triethyl, aluminium tribenzyl, tribenzoxy aluminium.  The preferred catalysts are those organo-metallic compounds with substituents R1, R2 or R3 of less than six carbon atoms and the particularly preferred compounds are those of aluminium, especially those of the formula AlR3 in which R is an alkyl group, e.g. aluminium triethyl and aluminium tri-isobutyl.  In an example phenol and isobutylene are autoclaved in the presence of aluminium triethyl to give a product containing 75-80% tri-butylated phenol.  In other examples the catalyst used is aluminium tri-isopropoxide and aluminium tri-ethyl or zinc-diethyl.